Irrigation Water and Food Safety:  A Glimpse into How Research is Approaching This Issue
M. Dana Harriger

Foodborne illness outbreaks associated with fresh fruits and vegetables continue to be a significant concern for the produce industry and the consumer.  Approximately 76 million people in the United States become ill from foodborne diseases annually, and over 40% of these cases are linked to fresh produce.   Most of these outbreaks have been traced to contamination of fresh produce with microbial pathogens arising from either animal or human feces.  In some cases, this fecal contamination occurs via poor agricultural practices, such as fertilizing produce fields with untreated manure or inappropriately treated compost.  However, in many cases, contamination of produce with microbial pathogens occurs from the use of irrigation water contaminated with microbial pathogens that cause human illnesses. Among the greatest concerns with human pathogens on fresh produce are enteric pathogens such as Escherichia coli (E. coli) and this therefore serves as the fecal indicator bacteria (FIB) concentration to measure safe levels of bacteria in irrigation water.  Compliance limits for E. coli as the FIB are set by the FDA in the Food Safety Modernization Act Produce Rule for microbiological safety and testing. Quantifiable levels of generic E. coli are utilized as an indicator of fecal contamination in water.  High generic E. coli concentrations can occur in any water supply including streams, canals, ponds and lakes and if used as irrigation water there may be pathogens present.  Based on this relationship, if levels of generic E. coli are high in your water then the chance of having a pathogenic strain increases and could pose a contamination risk when used to irrigate produce. 
Dynamic environmental conditions such as temperature, pH and oxygen levels are known to affect the bacteria concentrations in free-flowing bodies of water.  Rain events leading to high flow rates can also cause significant spikes in E. coli levels.  Since the best way to ensure food safety is to prevent pathogens from coming into contact with crops, all farmers should presumably know if their irrigation water is safe.  This is particularly important for produce that is consumed raw, since once produce becomes contaminated with microbial pathogens it is virtually impossible to remove this contamination with washing alone.   However, testing irrigation water for pathogens can be expensive and/or require special equipment and results can be misleading depending on when the water was tested and/or how frequently since we know the bacterial concentrations are not steady.
Wilson has been collaborating on longitudinal water quality studies with a research group from the USDA for 10 years and most recently the FDA along the Conococheague Creek.   This presentation will discuss the significance of the research being conducted in the Conococheague watershed and at our USDA research plot located on the Wilson farm.  The data from research that has been conducted and is currently underway is part of the broader body of research on microbial contamination in irrigation water and food safety.   The ultimate goal is to prevent outbreaks and improve overall safety of fresh produce.

Dr. Dana Harriger is a Professor of Biology and has been a member of Wilson’s science faculty since 1996 and has extensive experience in higher education and research. He received a Ph.D. in Biomedical Sciences and a M.S. in Biological Sciences from Wright State University and B.S. in Biology from Juniata College. Prior to coming to Wilson, he had a joint appointment as a Research Fellow at Shriner’s Burn Institute and Department of Transplantation Surgery at the University of Cincinnati where he conducted clinical studies with cultured skin substitutes. He is currently a Director at Large for the Pennsylvania Academy of Sciences and has served on the Boards of the Capital Area Science and Engineering Fair and the Pennsylvania Society for Biomedical Research. Most recently he served 6 years as a Counselor in the Biology Division of the Council for Undergraduate Research whose mission is to support and promote high-quality undergraduate student-faculty collaborative research and scholarship. He has been the director for sponsored projects including a STEM grant for Biology and Chemistry scholarships through the National Science Foundation and three grants from the Foundation for Enhancing Communities to provide a summer science institute for youth and professional development for teachers on the use of scientific instrumentation. He is currently a Co-PI conducting longitudinal research projects with the Environmental Microbial and Food Safety Laboratory of the USDA and Center for Food Safety and Applied Nutrition of the FDA. Although broadly trained in biology, Dr. Harriger’s research and teaching is at the cellular level including ultrastructure, cellular interactions and communication pathways. He teaches a wide range of courses at Wilson including General Biology, Nutrition, Cell Biology, Immunology and Developmental Biology.